Predictably useful dental implants had their beginnings in Sweden in the 1960's in work done by Per-Ingvar Br.ang.nemark, who discovered in 1952 that lab animals' bone cells would deposit mineralized bone directly on implanted titanium objects, thereby solidly attaching them to the surrounding bone. He is credited with coining the term osseointegration, which is now in common use, to identify this process. Since his discovery, thousands of titanium implants of mostly screw-type design have been inserted in people's toothless spaces to anchor prosthetic teeth. This implantation has been done almost exclusively by elevating the soft tissue, drilling a hole in bone, placing the implant in the hole, stitching the soft tissue back over the implant, waiting a period of months, re-opening the soft tissue, uncovering the implant and attaching a stud to project through the gum. If bone augmentation has been necessary, yet more operations have been required. If one counts the extraction surgery that leads to most toothless spaces, patients progressing from having teeth, to having a toothless space, to getting an implant and then fastening a prosthetic tooth onto the implant, must submit to at least 3 surgeries. The total rises to 5 if bone augmentation is required and done separately. The number of surgeries would be reduced to one if an implant with a visible trans-mucosal healing element to guide gingival healing, inserted immediately on tooth removal, would osseointegrate. If so, subsequent access to the implant would be non-surgical. Implantation with placement of trans-mucosal elements on extraction would mean that patients would experience fewer painful, expensive and time-consuming surgeries and avoid bone loss in extraction sites, which is associated with problems of appearance, comfort and insufficient bone volume for eventual implants. Furthermore, the patients' periods of wearing temporary prosthetic replacement teeth or doing without teeth altogether would be shorter.
The unpredictability of success with currently available immediate implantation technology has meant that only a small proportion of implants have been placed in tooth sockets immediately after teeth have been removed, and only a small proportion of those have had trans-mucosal elements placed at the time of surgery. The main reason for covering newly-inserted implants with soft tissue during the initial healing phase has been to prevent patients from applying enough force to implants to disrupt bone formation, but prevention of infection has also been a motive, as has been exclusion of mucosal or gingival cells from the implant sites. These potential causes of failure can be controlled without covering the implant initially. Infection prevention is easiest and does not require the present invention. Bacteria can be reduced or eliminated with surgical instruments, sterile technique, antibiotics and antibacterial rinses. Robert Pilliar and others from the University of Toronto have found that implant movements under 50.mu. can take place without osseointegration being affected. Achieving fixation great enough to keep movements within this range is dependent on gaining intimate adaptation of the implant to the bone of the extraction site and by controlling the size, duration and direction of dislodging forces applied to it. Intimacy of adaptation can be increased by reshaping the extraction site to conform to the implant shape and by forcing the implant tightly into place. A visible trans-mucosal healing abutment attached to the implant at the time of placement would require the patient to avoid biting on it or pushing on it with his tongue to keep implant movements under 50.mu.. However, it is not unlikely that patients who wished to reduce their numbers of surgeries would find it possible to avoid moving visible healing abutments attached to their implants in most situations.